1. Field of the Invention
The present invention relates to a mobile information terminal having a cover which serves also as a liquid crystal display device.
2. Description of the Related Art
Recently, as typified by a notebook-type personal computer, a mobile information terminal which uses an electric power charged in an internal battery so as to be operable without using a power cord and portable is becoming pervasive. In many mobile information terminals, mounted is a transmission liquid crystal display device which uses light emitted from a backlight. In order to improve the portability of a mobile information terminal, a battery is requested to have a long life period, and also to be light in weight.
FIG. 7 is a side view of a notebook-type personal computer of the conventional art. The notebook-type personal computer 1 has a configuration in which a cover 3 is connected to the main unit 2 via an axis 4 so that the cover 3 is movable.
First, the main unit 2 has a processing unit (not shown) such as a CPU, and a controlling unit (not shown) in a case. An input device 5 such as a keyboard is disposed on the surface of the main unit. The axis 4 for connecting the cover 3 is placed in one end portion of the main unit 2.
Next, the cover 3 is connected to the main unit 2 via the axis 4 disposed in an end portion 13, and has a liquid crystal display device 8 disposed in an outer case 12. The liquid crystal display device 8 is configured by a liquid crystal panel 14 and a backlight 15. The display screen of the liquid crystal panel 14 is exposed from the outer case 12 so as to be seen. The backlight 15 is placed on the rear face of the liquid crystal panel 14 to illuminate the liquid crystal panel 14 from the rear side. The liquid crystal panel 14 controls the transmission of the light of the backlight 15 to display an image. The backlight 15 is exposed from the outer case 12 so that the exposed portion functions as a light-introducing portion 30. The light-introducing portion 30 introduces external light such as sunlight or roomlight. The introduced external light can be used as light with which the backlight 15 illuminates the liquid crystal panel 14. The main unit 2 and the cover 3 are provided with a lock mechanism 6. The lock mechanism 6 is configured by a knob portion 6a, a hook portion 6b, and a hook hole so as to fix the main unit 2 and the cover 3 together when the cover 3 is closed. When the knob portion 6a is moved toward an end portion 9, the hook portion 6b is moved to be disengaged from the hook hole which is formed in a position of the cover 3 corresponding to the hook portion 6b, thereby allowing the cover 3 to be opened.
Next, the liquid crystal display device 8 will be described in detail. FIG. 8 is a section view of the cover 3. The liquid crystal display device 8 is positioned in the outer case 12, and configured by the liquid crystal panel 14 and the backlight 15. The liquid crystal panel 14 has a configuration in which a liquid crystal layer 21 is interposed between two substrates 23 made of a transparent insulative material such as glass. A polarizing plate 22 is disposed on the outside of each of the substrates 23. The polarizing plates 22 are placed so that their polarizing axes are perpendicular or parallel to each other. In the liquid crystal layer 21, the initial alignment of liquid crystal molecules (not shown) is determined by an alignment film. A voltage is applied across transparent electrodes (not shown) on the glass substrates 23 to change the alignment of the liquid crystal molecules in the liquid crystal layer 21, whereby the light transmittance is changed. As a result, the liquid crystal panel 14 can display an image.
The backlight 15 is configured by a light guide plate 26, a light source 27, a reflector plate 28, a diffusion plate 29, and a lens sheet (not shown). The light source 27 is a light source consisting of, for example, a cold cathode tube. The light guide plate 26 is made of a transparent resin such as an acrylic resin, and guides light emitted from the light source 27. An end portion of the light guide plate 26 which is opposed to the light source 27 is formed as the light-introducing portion 30 which is exposed from the outer case 12. The light-introducing portion 30 introduces external light such as sunlight or roomlight into the light guide plate 26. The light introduced into the light-introducing portion 30 is used as a light source in place of or auxiliary to the light source 27, so that it is reflected by the reflector plate 28 in the direction to the diffusion plate 29, formed into a surface light source by the diffusion plate 29, converged by the lens sheet (not shown), and then emitted from an illumination surface of the light guide plate 26 to impinge on the liquid crystal panel 14. When the external light is used as a light source in place of the light source 27, the power consumption of the light source 27 can be reduced. When the external light is used as a light source auxiliary to the light source 27, the brightness of the liquid crystal panel 14 can be enhanced so that the visibility of the liquid crystal panel 14 can be improved.
In the transmission liquid crystal display device which uses only the internal light source 27, the power consumed by the light source 27 amounts to 60 to 70% of the power consumption of the liquid crystal display device. As a result, the life period of the battery which supplies the power to the mobile information terminal is shortened, and hence the mobile information terminal cannot be carried for a long time period. When the size of a battery pack is increased in order to prolong the life period of the battery, the weight of the whole mobile information terminal is correspondingly increased to impair the portability of the terminal. Since the brightness of the backlight is lower than the brightness (illuminance) of external light, moreover, the visibility of the liquid crystal display device in outdoors is poor, thereby further impairing the portability of the mobile information terminal. In the above-mentioned mobile information terminal, the power consumption of the backlight 15 can be reduced by disposing the light-introducing portion 30, but the exposed area of the light-introducing portion 30 is small, thereby causing a problem in that the amount of external light which can be introduced is limited. In accordance with the recent tendency of thinning a notebook-type personal computer, particularly, also the light-introducing portion 30 must be further thinned. Therefore, the size of the light-introducing portion 30 is further reduced.
The invention has been conducted in order to solve the problems. It is an object of the invention to reduce the power consumption of a backlight and improve the visibility in outdoors, thereby improving the portability of a mobile information terminal.
The invention has been conducted in order to attain the object, and provides a mobile information terminal having a cover comprising: a liquid crystal panel; and a light-introducing portion which introduces external light to illuminate the liquid crystal panel, the cover being connected to a main unit by at least one axis to be movable, wherein one end of the cover including the light-introducing portion has a shape which, when the cover is closed and swung to a position where the cover overlaps with the main unit, covers an area of an end portion of the main unit opposed to the axis, the area extending from an upper face to a side face.
Furthermore, a mobile information terminal is provided in which the light-introducing portion is disposed in an end portion opposed to the axis, a length of the cover between the light-introducing portion and the axis is longer than a length of the main unit between an end portion opposed to the light-introducing portion and the axis, and a thickness of the cover in a position of the light-introducing portion is larger than a thickness of the cover in a position of the liquid crystal panel.
Furthermore, a mobile information terminal is provided in which a length of the cover between the light-introducing portion and the axis is longer than a length of the main unit between an end portion opposed to the light-introducing portion and the axis, and an end portion of the cover including the light-introducing portion has a shape which covers an end portion of the main unit opposed to the axis and extending from an upper face to a side face.
In these mobile information terminals, the end portion of the main unit opposed to the light-introducing portion is formed as a face inclined with respect to a bottom face of the main unit, and the light-introducing portion has a shape corresponding to the inclined face.